This invention relates to jig saws, and more particularly to portable electric jig saws of the type sometimes referred to as saber saws or bayonet saws.
Because jig saws of the present type are hand held by the operator, it is very important to provide as lightweight a mechanism as possible in order to reduce operator fatigue. Light weight is of particular significance with respect to the reciprocating or oscillating parts of the mechanism (such as the saw blade carrier) because excess weight in such parts causes excess vibration, and also requires excess counterbalancing which adds to overall weight.
Friction between the respective parts of the mechanism should also be minimized so that there is no excessive heat build-up, a major operator complaint. The saw blade support mechanisms of all jig saws are subject to a high twisting moment about the vertical axis of the blade due to the reacting forces exerted on the blade by the workpiece when the jig saw is being turned with respect to the workpiece. This twisting moment must be overcome by the blade support mechanism, but in many known mechanisms a substantial amount of undesirable frictional heat is created in the jig saw in accomplishing this.
A problem often encountered with non-orbital jig saws having a saw blade guide roller engaging the rearward edge of the blade, is that any misalignment between the carrier and roller in the fore-and-aft direction will cause the blade to be biased with respect to the carrier, which in turn can cause the blade to break, become loose and detach from the carrier, and/or damage the workpiece.
A primary object of the present invention resides in the provision of a portable jig saw ideally suited for heavy-duty professional use, yet which is relatively compact in size and light in weight, and which overcomes the aforementioned problems of known mechanisms.
Another object of the present invention resides in the provision of an improved lightweight, simple, one-piece saw blade carrier which is easy and inexpensive to manufacture, having minimum tolerance requirements. A related object concerns the provision of a unique three-point guide system for the saw blade carrier which renders the mechanism fully suitable for either non-orbital, orbital or adjustable orbit type jig saws, and automatically compensates for manufacturing tolerances while at all times providing a controlled guiding of the saw blade.
A further object of the present invention resides in the provision of an improved saw blade carrier and guide mechanism for non-orbital jig saws having a saw blade guide roller which significantly reduces the likelihood of blade breakage or detachment due to misalignment of the parts.
These and other objects, features and advantages of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings.